static <A, B> Map<A, B> cloneMap(Map<A, B> map) {
  if (map == null) ret new HashMap;
  // assume mutex is equal to map
  synchronized(map) {
    ret map instanceof TreeMap ? new TreeMap((TreeMap) map) // copies comparator
      : map instanceof LinkedHashMap ? new LinkedHashMap(map)
      : new HashMap(map);
  }
}

static <A, B> L<B> cloneMap(Iterable<A> l, IF1<A, B> f) {
  L x = emptyList(l);
  if (l != null) for (A o : cloneList(l))
    x.add(f.get(o));
  ret x;
}